The dexterity, reversibility, and reconfigurability of a complex shape or surface would enhance devices and practices in medicine, robotics, and aerospace. Limited complex shape change and actuation has been reported in patterned hydrogels by carefully designing semicrystalline polymer networks. The implementation of a programmable shape change in applications in aerospace and other outlets requires the further development of soft materials that exhibit large stimuli-induced responses while affording local control of the magnitudes and directionality of the strain. Once realized, these shape-programmable materials could enable and extend the functionality of devices in applications as simple as packaging to as complex as deployable and tunable antennas.
Cross-linked liquid crystal polymers, particularly elastomeric versions referred to as liquid crystal elastomers (“LCEs”) have shown some promise in the field of reconfigurable shapes and surfaces. LCEs are lightly cross-linked, ordered polymers that exhibit reversible shape change in response to a stimulus, such as heat, light, or solvent. Alignment of LCEs into a mono-domain or single crystal orientation has primarily employed stretching (the so-called “Finkelmann Method”) or applications of a magnetic field. Uniaxially-aligned LCEs have exhibited dimensional changes (tensile strain) that can exceed 300% along an alignment direction when exposed to a change in temperature.
However, these alignment methods are limited in spatial control of orientation and resolution. Complex director profiles within LCEs are necessary to realize monolithic devices or functional substrates capable of non-trivial, programmable, reversible shape change. While conventional methods exist and have been employed to generate complex and spatial variations in director orientations of low molar mass liquid crystals and glassy liquid crystalline polymer networks, the chemistries and procedures employed to synthesize aligned LCEs have proven insensitive to such techniques. Thus there remains a need for improved materials and methods for employing LCEs as reconfigurable shapes and surfaces.